Balancing the magnetosphere's magnetic flux budget

Many bodies in the universe have their own magnetic fields. The Sun's magnetic field extends out to the furthest reaches of the Solar System, and the magnetic field of a magnetised planet carves out a region of space called the planet's "magnetosphere". It is the interplay between the magnetic fields of the Sun and the Earth's magnetosphere that transfers huge amounts of energy and drives most of the activity within the magnetosphere. In this study, I will gain a more comprehensive understanding of the fundamental processes driving this response. However, a wider application of the science in this field is the ever-improving forecasts of space weather (the conditions in near-Earth space). This is of real importance in the modern age, with our reliance on satellites and other technologies that are sensitive to solar activity.

We know broadly how the region of space near Earth responds to solar activity. The Sun continuously spews out a hot gas (a plasma) called the solar wind, which flows through the Solar System. As it does so, it carries the Sun's magnetic field with it. The Earth's magnetic field protects us from the solar wind by forming a cavity called the magnetosphere. As the solar wind buffets the magnetosphere, the Sun's and Earth's magnetic fields collide. Sometimes, the two magnetic fields interlock and become connected in a process called 'reconnection'. This transfers energy from the Sun to the magnetosphere. This energy drives a lot of dynamic processes in the magnetosphere, such as increases in the intensity of the Van Allen radiation belts and geomagnetic storms, which can damage satellites and infrastructure on the ground. When the energy is released energetic particles are deposited into the atmosphere. This gives off light in an oval-shaped band around the North Pole and another around the South Pole which is called the 'aurora' or the northern and southern lights. (In the north, the oval usually stretches through Scandinavia, Siberia, Alaska and Canada, which is why these are the best places to see the northern lights.)

Many parts of this chain of events are poorly understood, and I will make advances in two key areas. Firstly, we do not understand exactly how the 'interlocking' process happens. We cannot even agree how much interlocking takes place; people have tried to measure this by using satellites and radars that see the effects in the ionosphere (a layer of the upper atmosphere), and get wildly different answers. By taking a new approach developed from some of my recent work, I will be able to measure this effect accurately; I am confident that my estimates from spacecraft and ionospheric measurements will agree.

The second aspect I will study is how the magnetosphere behaves when the Earth's and Sun's magnetic fields do not interlock. We know that under these conditions auroras form in a different way - rather than just forming in an oval around the pole, they are also seen at higher latitudes. We do not fully comprehend how high latitude auroras are formed, or how the magnetosphere behaves under these conditions. By making measurements of both the aurora and the environment in the magnetosphere, I will be able to work this out.

These two questions are different sides to the problem of understanding how our environment is driven by the solar wind. Gaining a thorough understanding of this is important for two reasons. First, space weather forecasting requires a detailed knowledge of how the magnetosphere works and how it responds to the solar wind. Second, the 'interlocking' process (reconnection) occurs throughout the universe, and so understanding it is vital if we are to comprehend the workings of a large number of astronomical objects. The quality and range of measurements that can be made in the magnetosphere make it the best place to observe and understand reconnection.